qlist.qdoc

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// Copyright (C) 2020 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
 
/*!
    \class QVector
    \inmodule QtCore
    \brief QVector is an alias for QList.
 
    Please see the QList documentation for details.
*/
 
/*!
    \class QList
    \inmodule QtCore
    \brief The QList class is a template class that provides a dynamic array.
 
    \ingroup tools
    \ingroup shared
 
    \reentrant
 
    QList<T> is one of Qt's generic \l{container classes}. It
    stores its items in adjacent memory locations and provides fast
    index-based access. QVector<T> used to be a different class in
    Qt 5, but is now a simple alias to QList.
 
    QList<T> and QVarLengthArray<T>
    provide similar APIs and functionality. They are often interchangeable,
    but there are performance consequences. Here is an overview of use cases:
 
    \list
    \li QList should be your default first choice.
    \li QVarLengthArray provides an array that reserves space on the stack,
        but can dynamically grow onto the heap if required. It's good to
        use for short lived containers that are usually small.
    \li If you need a real linked list, which guarantees
        \l{Algorithmic Complexity}{constant time} insertions mid-list and
        uses iterators to items rather than indexes, use std::list.
    \endlist
 
    \note QList and QVarLengthArray both guarantee C-compatible
    array layout.
    \note QList in Qt 5 did not always have a C-compatible array layout and
    we often recommended to use QVector instead for more predictable
    performance. This is not the case in Qt 6 anymore, where both classes
    now share an implementation and can be used interchangeably.
 
    Here's an example of a QList that stores integers and a QList
    that stores QString values:
 
    \snippet code/src_corelib_tools_qlist.cpp 0
 
    QList stores its items in an array of continuous memory. Typically, lists
    are created with an initial size. For example, the following code
    constructs a QList with 200 elements:
 
    \snippet code/src_corelib_tools_qlist.cpp 1
 
    The elements are automatically initialized with a
    \l{default-constructed value}. If you want to initialize the
    list with a different value, pass that value as the second
    argument to the constructor:
 
    \snippet code/src_corelib_tools_qlist.cpp 2
 
    You can also call fill() at any time to fill the list with a
    value.
 
    QList uses 0-based indexes, just like C++ arrays. To access the
    item at a particular index position, you can use operator[](). On
    non-const lists, operator[]() returns a reference to the item
    that can be used on the left side of an assignment:
 
    \snippet code/src_corelib_tools_qlist.cpp 3
 
    For read-only access, an alternative syntax is to use at():
 
    \snippet code/src_corelib_tools_qlist.cpp 4
 
    at() can be faster than operator[](), because it never causes a
    \l{deep copy} to occur.
 
    Another way to access the data stored in a QList is to call
    data(). The function returns a pointer to the first item in the
    list. You can use the pointer to directly access and modify the
    elements stored in the list. The pointer is also useful if you
    need to pass a QList to a function that accepts a plain C++
    array.
 
    If you want to find all occurrences of a particular value in a
    list, use indexOf() or lastIndexOf(). The former searches
    forward starting from a given index position, the latter searches
    backward. Both return the index of the matching item if they found
    one; otherwise, they return -1. For example:
 
    \snippet code/src_corelib_tools_qlist.cpp 5
 
    If you simply want to check whether a list contains a
    particular value, use contains(). If you want to find out how
    many times a particular value occurs in the list, use count().
 
    QList provides these basic functions to add, move, and remove
    items: insert(), replace(), remove(), prepend(), append(). With the
    exception of append(), prepend() and replace(), these functions can be slow
    (\l{linear time}) for large lists, because they require moving many items in
    the list by one position in memory. If you want a container class that
    provides fast insertion/removal in the middle, use std::list instead.
 
    Unlike plain C++ arrays, QLists can be resized at any time by
    calling resize(). If the new size is larger than the old size,
    QList might need to reallocate the whole list. QList tries
    to reduce the number of reallocations by preallocating up to twice
    as much memory as the actual data needs.
 
    If you're building a QList gradually and know in advance
    approximately how many elements it will contain, you can call reserve(),
    asking QList to preallocate a certain amount of memory.
    You can also call capacity() to find out how much memory the
    QList actually has allocated.
 
    Note that using non-const operators and functions can cause QList
    to do a deep copy of the data, due to \l{implicit sharing}.
 
    QList's value type must be an \l{assignable data type}. This
    covers most data types that are commonly used, but the compiler
    won't let you, for example, store a QWidget as a value; instead,
    store a QWidget *. A few functions have additional requirements;
    for example, indexOf() and lastIndexOf() expect the value type to
    support \c operator==().  These requirements are documented on a
    per-function basis.
 
    For iterating over the items, see \l {Iterating over Containers}.
 
    In addition to QList, Qt also provides QVarLengthArray, a very
    low-level class with little functionality that is optimized for
    speed.
 
    \section2 More Information on Using Qt Containers
 
    For a detailed discussion comparing Qt containers with each other and
    with STL containers, see \l {Understand the Qt Containers}.
 
    \section1 Maximum size and out-of-memory conditions
 
    The maximum size of QList depends on the architecture. Most 64-bit
    systems can allocate more than 2 GB of memory, with a typical limit
    of 2^63 bytes. The actual value also depends on the overhead required for
    managing the data block. As a result, you can expect the maximum size
    of 2 GB minus overhead on 32-bit platforms, and 2^63 bytes minus overhead
    on 64-bit platforms. The number of elements that can be stored in a
    QList is this maximum size divided by the size of a stored element.
 
    When memory allocation fails, QList uses the \l Q_CHECK_PTR macro,
    which throws a \c std::bad_alloc exception if the application is being
    compiled with exception support. If exceptions are disabled, then running
    out of memory is undefined behavior.
 
    Note that the operating system may impose further limits on applications
    holding a lot of allocated memory, especially large, contiguous blocks.
    Such considerations, the configuration of such behavior or any mitigation
    are outside the scope of the Qt API.
*/
 
/*!
    \fn template <typename T> QList<T> QList<T>::mid(qsizetype pos, qsizetype length = -1) const
 
    Returns a sub-list which contains elements from this list,
    starting at position \a pos. If \a length is -1 (the default), all
    elements after \a pos are included; otherwise \a length elements (or
    all remaining elements if there are less than \a length elements)
    are included.
*/
 
/*!
    \fn template <typename T> QList<T> QList<T>::first(qsizetype n) const
    \since 6.0
 
    Returns a sub-list that contains the first \a n elements
    of this list.
 
    \note The behavior is undefined when \a n < 0 or \a n > size().
 
    \sa last(), sliced()
*/
 
/*!
    \fn template <typename T> QList<T> QList<T>::last(qsizetype n) const
    \since 6.0
 
    Returns a sub-list that contains the last \a n elements of this list.
 
    \note The behavior is undefined when \a n < 0 or \a n > size().
 
    \sa first(), sliced()
*/
 
/*!
    \fn template <typename T> QList<T> QList<T>::sliced(qsizetype pos, qsizetype n) const
    \since 6.0
 
    Returns a sub-list that contains \a n elements of this list,
    starting at position \a pos.
 
    \note The behavior is undefined when \a pos < 0, \a n < 0,
    or \a pos + \a n > size().
 
    \sa first(), last()
*/
 
/*!
    \fn template <typename T> QList<T> QList<T>::sliced(qsizetype pos) const
    \since 6.0
    \overload
 
    Returns a sub-list that contains the elements of this list starting at
    position \a pos and extending to its end.
 
    \note The behavior is undefined when \a pos < 0 or \a pos > size().
 
    \sa first(), last()
*/
 
 
/*! \fn template <typename T> QList<T>::QList()
 
    Constructs an empty list.
 
    \sa resize()
*/
 
/*!
    \fn template <typename T> QList<T>::QList(QList<T> &&other)
 
    Move-constructs a QList instance, making it point at the same
    object that \a other was pointing to.
 
    \since 5.2
*/
 
/*! \fn template <typename T> QList<T>::QList(qsizetype size)
 
    Constructs a list with an initial size of \a size elements.
 
    The elements are initialized with a \l{default-constructed
    value}.
 
    \sa resize()
*/
 
/*! \fn template <typename T> QList<T>::QList(qsizetype size, parameter_type value)
 
    Constructs a list with an initial size of \a size elements.
    Each element is initialized with \a value.
 
    \sa resize(), fill()
*/
 
/*! \fn template <typename T> QList<T>::QList(const QList<T> &other)
 
    Constructs a copy of \a other.
 
    This operation takes \l{Algorithmic Complexity}{constant time},
    because QList is \l{implicitly shared}. This makes returning
    a QList from a function very fast. If a shared instance is
    modified, it will be copied (copy-on-write), and that takes
    \l{Algorithmic Complexity}{linear time}.
 
    \sa operator=()
*/
 
/*! \fn template <typename T> QList<T>::QList(std::initializer_list<T> args)
    \since 4.8
 
    Constructs a list from the std::initializer_list given by \a args.
*/
 
/*! \fn template <typename T> template<typename InputIterator, if_input_iterator<InputIterator>> QList<T>::QList(InputIterator first, InputIterator last)
    \since 5.14
 
    Constructs a list with the contents in the iterator range [\a first, \a last).
 
    \note This constructor only participates in overload resolution if
    \c InputIterator meets the requirements of a
    \l {https://en.cppreference.com/w/cpp/named_req/InputIterator} {LegacyInputIterator}.
 
    The value type of \c InputIterator must be convertible to \c T.
*/
 
/*! \fn template <typename T> QList<T>::~QList()
 
    Destroys the list.
*/
 
/*! \fn template <typename T> QList<T> &QList<T>::operator=(const QList<T> &other)
 
    Assigns \a other to this list and returns a reference to this
    list.
*/
 
/*!
    \fn template <typename T> QList<T> &QList<T>::operator=(QList<T> &&other)
 
    Move-assigns \a other to this QList instance.
 
    \since 5.2
*/
 
/*!
    \fn template <typename T> QList<T> &QList<T>::operator=(std::initializer_list<T> args)
    \since 5.14
 
    Assigns the collection of values in \a args to this QList instance.
*/
 
/*! \fn template <typename T> void QList<T>::swap(QList<T> &other)
    \since 4.8
 
    Swaps list \a other with this list. This operation is very fast and
    never fails.
*/
 
/*! \fn template <typename T> void QList<T>::swapItemsAt(qsizetype i, qsizetype j)
 
    Exchange the item at index position \a i with the item at index
    position \a j. This function assumes that both \a i and \a j are
    at least 0 but less than size(). To avoid failure, test that both
    \a i and \a j are at least 0 and less than size().
*/
 
 
/*! \fn template <typename T> bool QList<T>::operator==(const QList<T> &other) const
 
    Returns \c true if \a other is equal to this list; otherwise
    returns \c false.
 
    Two lists are considered equal if they contain the same values
    in the same order.
 
    This function requires the value type to have an implementation
    of \c operator==().
 
    \sa operator!=()
*/
 
/*! \fn template <typename T> bool QList<T>::operator!=(const QList<T> &other) const
 
    Returns \c true if \a other is not equal to this list; otherwise
    returns \c false.
 
    Two lists are considered equal if they contain the same values
    in the same order.
 
    This function requires the value type to have an implementation
    of \c operator==().
 
    \sa operator==()
*/
 
/*! \fn template <typename T> bool QList<T>::operator<(const QList<T> &other) const
    \since 5.6
 
    Returns \c true if this list is
    \l{http://en.cppreference.com/w/cpp/algorithm/lexicographical_compare}
    {lexically less than} \a other; otherwise returns \c false.
 
    This function requires the value type to have an implementation
    of \c operator<().
*/
 
/*! \fn template <typename T> bool QList<T>::operator<=(const QList<T> &other) const
    \since 5.6
 
    Returns \c true if this list is
    \l{http://en.cppreference.com/w/cpp/algorithm/lexicographical_compare}
    {lexically less than or equal to} \a other; otherwise returns \c false.
 
    This function requires the value type to have an implementation
    of \c operator<().
*/
 
/*! \fn template <typename T> bool QList<T>::operator>(const QList<T> &other) const
    \since 5.6
 
    Returns \c true if this list is
    \l{http://en.cppreference.com/w/cpp/algorithm/lexicographical_compare}
    {lexically greater than} \a other; otherwise returns \c false.
 
    This function requires the value type to have an implementation
    of \c operator<().
*/
 
/*! \fn template <typename T> bool QList<T>::operator>=(const QList<T> &other) const
    \since 5.6
 
    Returns \c true if this list is
    \l{http://en.cppreference.com/w/cpp/algorithm/lexicographical_compare}
    {lexically greater than or equal to} \a other; otherwise returns \c false.
 
    This function requires the value type to have an implementation
    of \c operator<().
*/
 
/*!
    \fn template <typename T> size_t qHash(const QList<T> &key, size_t seed = 0)
    \since 5.6
    \relates QList
 
    Returns the hash value for \a key,
    using \a seed to seed the calculation.
 
    This function requires qHash() to be overloaded for the value type \c T.
*/
 
/*! \fn template <typename T> qsizetype QList<T>::size() const
 
    Returns the number of items in the list.
 
    \sa isEmpty(), resize()
*/
 
/*! \fn template <typename T> bool QList<T>::isEmpty() const
 
    Returns \c true if the list has size 0; otherwise returns \c false.
 
    \sa size(), resize()
*/
 
/*! \fn template <typename T> void QList<T>::resize(qsizetype size)
    \since 6.0
 
    Sets the size of the list to \a size. If \a size is greater than the
    current size, elements are added to the end; the new elements are
    initialized with a \l{default-constructed value}. If \a size is less
    than the current size, elements are removed from the end.
 
    If this list is not shared, the capacity() is preserved. Use squeeze()
    to shed excess capacity.
 
    \note In Qt versions prior to 5.7 (for QVector; QList lacked a resize()
    until 6.0), this function released the memory used by the list instead of
    preserving the capacity.
 
    \sa size()
*/
 
/*! \fn template <typename T> qsizetype QList<T>::capacity() const
 
    Returns the maximum number of items that can be stored in the
    list without forcing a reallocation.
 
    The sole purpose of this function is to provide a means of fine
    tuning QList's memory usage. In general, you will rarely ever
    need to call this function. If you want to know how many items are
    in the list, call size().
 
    \note a statically allocated list will report a capacity of 0,
    even if it's not empty.
 
    \warning The free space position in the allocated memory block is undefined.
    In other words, you should not assume that the free memory is always located
    at the end of the list. You can call reserve() to ensure that there is
    enough space at the end.
 
    \sa reserve(), squeeze()
*/
 
/*! \fn template <typename T> void QList<T>::reserve(qsizetype size)
 
    Attempts to allocate memory for at least \a size elements.
 
    If you know in advance how large the list will be, you should call this
    function to prevent reallocations and memory fragmentation. If you resize
    the list often, you are also likely to get better performance.
 
    If in doubt about how much space shall be needed, it is usually better to
    use an upper bound as \a size, or a high estimate of the most likely size,
    if a strict upper bound would be much bigger than this. If \a size is an
    underestimate, the list will grow as needed once the reserved size is
    exceeded, which may lead to a larger allocation than your best overestimate
    would have and will slow the operation that triggers it.
 
    \warning reserve() reserves memory but does not change the size of the
    list. Accessing data beyond the current end of the list is
    undefined behavior. If you need to access memory beyond the current end of
    the list, use resize().
 
    \sa squeeze(), capacity(), resize()
*/
 
/*! \fn template <typename T> void QList<T>::squeeze()
 
    Releases any memory not required to store the items.
 
    The sole purpose of this function is to provide a means of fine
    tuning QList's memory usage. In general, you will rarely ever
    need to call this function.
 
    \sa reserve(), capacity()
*/
 
/*! \fn template <typename T> void QList<T>::detach()
 
    \internal
*/
 
/*! \fn template <typename T> bool QList<T>::isDetached() const
 
    \internal
*/
 
/*! \fn template <typename T> void QList<T>::setSharable(bool sharable)
 
    \internal
*/
 
/*! \fn template <typename T> bool QList<T>::isSharedWith(const QList<T> &other) const
 
    \internal
*/
 
/*! \fn template <typename T> T *QList<T>::data()
 
    Returns a pointer to the data stored in the list. The pointer
    can be used to access and modify the items in the list.
 
    Example:
    \snippet code/src_corelib_tools_qlist.cpp 6
 
    \warning The pointer is invalidated on detachment or when the QList is
    modified.
 
    This function is mostly useful to pass a list to a function
    that accepts a plain C++ array.
 
    \sa constData(), operator[]()
*/
 
/*! \fn template <typename T> const T *QList<T>::data() const
 
    \overload
*/
 
/*! \fn template <typename T> const T *QList<T>::constData() const
 
    Returns a const pointer to the data stored in the list. The
    pointer can be used to access the items in the list.
 
    \warning The pointer is invalidated on detachment or when the QList is
    modified.
 
    This function is mostly useful to pass a list to a function
    that accepts a plain C++ array.
 
    \sa data(), operator[]()
*/
 
/*! \fn template <typename T> void QList<T>::clear()
 
    Removes all the elements from the list.
 
    If this list is not shared, the capacity() is preserved. Use squeeze() to
    shed excess capacity.
 
    \note In Qt versions prior to 5.7 (for QVector) and 6.0 (for QList), this
    function released the memory used by the list instead of preserving the
    capacity.
 
    \sa resize(), squeeze()
*/
 
/*! \fn template <typename T> const T &QList<T>::at(qsizetype i) const
 
    Returns the item at index position \a i in the list.
 
    \a i must be a valid index position in the list (i.e., 0 <= \a
    i < size()).
 
    \sa value(), operator[]()
*/
 
/*! \fn template <typename T> T &QList<T>::operator[](qsizetype i)
 
    Returns the item at index position \a i as a modifiable reference.
 
    \a i must be a valid index position in the list (i.e., 0 <= \a i
    < size()).
 
    Note that using non-const operators can cause QList to do a deep
    copy.
 
    \sa at(), value()
*/
 
/*! \fn template <typename T> const T &QList<T>::operator[](qsizetype i) const
 
    \overload
 
    Same as at(\a i).
*/
 
/*!
    \fn template <typename T> void QList<T>::append(parameter_type value)
 
    Inserts \a value at the end of the list.
 
    Example:
    \snippet code/src_corelib_tools_qlist.cpp 7
 
    This is the same as calling resize(size() + 1) and assigning \a
    value to the new last element in the list.
 
    This operation is relatively fast, because QList typically
    allocates more memory than necessary, so it can grow without
    reallocating the entire list each time.
 
    \sa operator<<(), prepend(), insert()
*/
 
/*!
    \fn template <typename T> void QList<T>::append(rvalue_ref value)
    \since 5.6
 
    \overload
 
    Example:
    \snippet code/src_corelib_tools_qlist.cpp move-append
*/
 
/*! \fn template <typename T> void QList<T>::append(const QList<T> &value)
 
    \overload
 
    \since 5.5
 
    Appends the items of the \a value list to this list.
 
    \sa operator<<(), operator+=()
*/
 
/*! \fn template <typename T> void QList<T>::append(QList<T> &&value)
    \overload
 
    \since 6.0
 
    Moves the items of the \a value list to the end of this list.
 
    \sa operator<<(), operator+=()
*/
 
/*!
    \fn template <typename T> void QList<T>::prepend(parameter_type value)
    \fn template <typename T> void QList<T>::prepend(rvalue_ref value)
 
    Inserts \a value at the beginning of the list.
 
    Example:
    \snippet code/src_corelib_tools_qlist.cpp 8
 
    This is the same as list.insert(0, \a value).
 
    Normally this operation is relatively fast (amortized \l{constant time}).
    QList is able to allocate extra memory at the beginning of the list data
    and grow in that direction without reallocating or moving the data on each
    operation. However if you want a container class with a guarantee of
    \l{constant time} prepend, use std::list instead,
    but prefer QList otherwise.
 
    \sa append(), insert()
*/
 
/*!
    \fn template <typename T> template <typename ...Args> T &QList<T>::emplaceBack(Args&&... args)
    \fn template <typename T> template <typename ...Args> T &QList<T>::emplace_back(Args&&... args)
 
    Adds a new element to the end for the container. This new element
    is constructed in-place using \a args as the arguments for its
    construction.
 
    Returns a reference to the new element.
 
    Example:
    \snippet code/src_corelib_tools_qlist.cpp emplace-back
 
    It is also possible to access a newly created object by using
    returned reference:
    \snippet code/src_corelib_tools_qlist.cpp emplace-back-ref
 
    This is the same as list.emplace(list.size(), \a args).
 
    \sa emplace
*/
 
/*! \fn template <typename T> void QList<T>::insert(qsizetype i, parameter_type value)
    \fn template <typename T> void QList<T>::insert(qsizetype i, rvalue_ref value)
 
    Inserts \a value at index position \a i in the list. If \a i is
    0, the value is prepended to the list. If \a i is size(), the
    value is appended to the list.
 
    Example:
    \snippet code/src_corelib_tools_qlist.cpp 9
 
    For large lists, this operation can be slow (\l{linear time}),
    because it requires moving all the items at indexes \a i and
    above by one position further in memory. If you want a container
    class that provides a fast insert() function, use std::list
    instead.
 
    \sa append(), prepend(), remove()
*/
 
/*! \fn template <typename T> void QList<T>::insert(qsizetype i, qsizetype count, parameter_type value)
 
    \overload
 
    Inserts \a count copies of \a value at index position \a i in the
    list.
 
    Example:
    \snippet code/src_corelib_tools_qlist.cpp 10
*/
 
/*! \fn template <typename T> QList<T>::iterator QList<T>::insert(const_iterator before, parameter_type value)
    \fn template <typename T> QList<T>::iterator QList<T>::insert(const_iterator before, rvalue_ref value)
 
    \overload
 
    Inserts \a value in front of the item pointed to by the iterator
    \a before. Returns an iterator pointing at the inserted item.
*/
 
/*! \fn template <typename T> QList<T>::iterator QList<T>::insert(const_iterator before, qsizetype count, parameter_type value)
 
    Inserts \a count copies of \a value in front of the item pointed to
    by the iterator \a before. Returns an iterator pointing at the
    first of the inserted items.
*/
 
/*!
    \fn template <typename T> template <typename ...Args> QList<T>::iterator QList<T>::emplace(qsizetype i, Args&&... args)
 
    Extends the container by inserting a new element at position \a i.
    This new element is constructed in-place using \a args as the
    arguments for its construction.
 
    Returns an iterator to the new element.
 
    Example:
    \snippet code/src_corelib_tools_qlist.cpp emplace
 
    \note It is guaranteed that the element will be created in place
          at the beginning, but after that it might be copied or
          moved to the right position.
 
    \sa emplaceBack
*/
 
 
/*! \fn template <typename T> void QList<T>::replace(qsizetype i, parameter_type value)
    \fn template <typename T> void QList<T>::replace(qsizetype i, rvalue_ref value)
 
    Replaces the item at index position \a i with \a value.
 
    \a i must be a valid index position in the list (i.e., 0 <= \a
    i < size()).
 
    \sa operator[](), remove()
*/
 
/*! \fn template <typename T> void QList<T>::remove(qsizetype i, qsizetype n = 1)
 
    Removes \a n elements from the list, starting at index position \a i.
 
//! [shrinking-erase]
    Element removal will preserve the list's capacity and not reduce the amount of
    allocated memory. To shed extra capacity and free as much memory as possible,
    call squeeze().
//! [shrinking-erase]
 
//! [iterator-invalidation-erase]
    \note When QList is not \l{implicitly shared}, this function only
    invalidates iterators at or after the specified position.
//! [iterator-invalidation-erase]
 
    \sa insert(), replace(), fill()
*/
 
/*! \fn template <typename T> void QList<T>::removeAt(qsizetype i)
    \since 5.2
 
    Removes the element at index position \a i.
    Equivalent to
    \code
    remove(i);
    \endcode
 
    \include qlist.qdoc shrinking-erase
    \include qlist.qdoc iterator-invalidation-erase
 
    \sa remove()
*/
 
/*! \fn template <typename T> template <typename AT = T> qsizetype QList<T>::removeAll(const AT &t)
    \since 5.4
 
    Removes all elements that compare equal to \a t from the
    list. Returns the number of elements removed, if any.
 
    \include qlist.qdoc shrinking-erase
 
    \sa removeOne()
*/
 
/*! \fn template <typename T> template <typename AT = T> bool QList<T>::removeOne(const AT &t)
    \since 5.4
 
    Removes the first element that compares equal to \a t from the
    list. Returns whether an element was, in fact, removed.
 
    \include qlist.qdoc shrinking-erase
 
    \sa removeAll()
*/
 
/*! \fn template <typename T> template <typename Predicate> qsizetype QList<T>::removeIf(Predicate pred)
    \since 6.1
 
    Removes all elements for which the predicate \a pred returns true
    from the list. Returns the number of elements removed, if any.
 
    \sa removeAll()
*/
 
/*! \fn template <typename T> qsizetype QList<T>::length() const
    \since 5.2
 
    Same as size() and count().
 
    \sa size(), count()
*/
 
/*! \fn template <typename T> T QList<T>::takeAt(qsizetype i)
    \since 5.2
 
    Removes the element at index position \a i and returns it.
 
    Equivalent to
    \code
    T t = at(i);
    remove(i);
    return t;
    \endcode
 
    \include qlist.qdoc iterator-invalidation-erase
 
    \sa takeFirst(), takeLast()
*/
 
/*! \fn template <typename T> void QList<T>::move(qsizetype from, qsizetype to)
    \since 5.6
 
    Moves the item at index position \a from to index position \a to.
*/
 
/*! \fn template <typename T> void QList<T>::removeFirst()
    \since 5.1
    Removes the first item in the list. Calling this function is
    equivalent to calling remove(0). The list must not be empty. If
    the list can be empty, call isEmpty() before calling this
    function.
 
    \include qlist.qdoc shrinking-erase
 
    \sa remove(), takeFirst(), isEmpty()
*/
 
/*! \fn template <typename T> void QList<T>::removeLast()
    \since 5.1
    Removes the last item in the list. Calling this function is
    equivalent to calling remove(size() - 1). The list must not be
    empty. If the list can be empty, call isEmpty() before calling
    this function.
 
    \include qlist.qdoc shrinking-erase
 
    \sa remove(), takeLast(), removeFirst(), isEmpty()
*/
 
/*! \fn template <typename T> T QList<T>::takeFirst()
    \since 5.1
 
    Removes the first item in the list and returns it. This function
    assumes the list is not empty. To avoid failure, call isEmpty()
    before calling this function.
 
    \sa takeLast(), removeFirst()
*/
 
/*! \fn template <typename T> T QList<T>::takeLast()
    \since 5.1
 
    Removes the last item in the list and returns it. This function
    assumes the list is not empty. To avoid failure, call isEmpty()
    before calling this function.
 
    If you don't use the return value, removeLast() is more
    efficient.
 
    \sa takeFirst(), removeLast()
*/
 
/*!
    \fn template <typename T> template <typename ...Args> QList<T>::iterator QList<T>::emplace(const_iterator before, Args&&... args)
 
    \overload
 
    Creates a new element in front of the item pointed to by the
    iterator \a before. This new element is constructed in-place
    using \a args as the arguments for its construction.
 
    Returns an iterator to the new element.
*/
 
/*! \fn template <typename T> QList<T> &QList<T>::fill(parameter_type value, qsizetype size = -1)
 
    Assigns \a value to all items in the list. If \a size is
    different from -1 (the default), the list is resized to \a size beforehand.
 
    Example:
    \snippet code/src_corelib_tools_qlist.cpp 11
 
    \sa resize()
*/
 
/*! \fn template <typename T> template <typename AT = T> qsizetype QList<T>::indexOf(const AT &value, qsizetype from = 0) const
 
    Returns the index position of the first occurrence of \a value in
    the list, searching forward from index position \a from.
    Returns -1 if no item matched.
 
    Example:
    \snippet code/src_corelib_tools_qlist.cpp 12
 
    This function requires the value type to have an implementation of
    \c operator==().
 
    \sa lastIndexOf(), contains()
*/
 
/*! \fn template <typename T> template <typename AT = T> qsizetype QList<T>::lastIndexOf(const AT &value, qsizetype from = -1) const
 
    Returns the index position of the last occurrence of the value \a
    value in the list, searching backward from index position \a
    from. If \a from is -1 (the default), the search starts at the
    last item. Returns -1 if no item matched.
 
    Example:
    \snippet code/src_corelib_tools_qlist.cpp 13
 
    This function requires the value type to have an implementation of
    \c operator==().
 
    \sa indexOf()
*/
 
/*! \fn template <typename T> template <typename AT = T> bool QList<T>::contains(const AT &value) const
 
    Returns \c true if the list contains an occurrence of \a value;
    otherwise returns \c false.
 
    This function requires the value type to have an implementation of
    \c operator==().
 
    \sa indexOf(), count()
*/
 
/*! \fn template <typename T> bool QList<T>::startsWith(parameter_type value) const
    \since 4.5
 
    Returns \c true if this list is not empty and its first
    item is equal to \a value; otherwise returns \c false.
 
    \sa isEmpty(), first()
*/
 
/*! \fn template <typename T> bool QList<T>::endsWith(parameter_type value) const
    \since 4.5
 
    Returns \c true if this list is not empty and its last
    item is equal to \a value; otherwise returns \c false.
 
    \sa isEmpty(), last()
*/
 
 
/*! \fn template <typename T> template <typename AT = T> qsizetype QList<T>::count(const AT &value) const
 
    Returns the number of occurrences of \a value in the list.
 
    This function requires the value type to have an implementation of
    \c operator==().
 
    \sa contains(), indexOf()
*/
 
/*! \fn template <typename T> qsizetype QList<T>::count() const
 
    \overload
 
    Same as size().
*/
 
/*! \fn template <typename T> QList<T>::iterator QList<T>::begin()
 
    Returns an \l{STL-style iterators}{STL-style iterator} pointing to the
    first item in the list.
 
//! [iterator-invalidation-func-desc]
    \warning The returned iterator is invalidated on detachment or when the
    QList is modified.
//! [iterator-invalidation-func-desc]
 
    \sa constBegin(), end()
*/
 
/*! \fn template <typename T> QList<T>::const_iterator QList<T>::begin() const
 
    \overload
*/
 
/*! \fn template <typename T> QList<T>::const_iterator QList<T>::cbegin() const
    \since 5.0
 
    Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the
    first item in the list.
 
    \include qlist.qdoc iterator-invalidation-func-desc
 
    \sa begin(), cend()
*/
 
/*! \fn template <typename T> QList<T>::const_iterator QList<T>::constBegin() const
 
    Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the
    first item in the list.
 
    \include qlist.qdoc iterator-invalidation-func-desc
 
    \sa begin(), constEnd()
*/
 
/*! \fn template <typename T> QList<T>::iterator QList<T>::end()
 
    Returns an \l{STL-style iterators}{STL-style iterator} pointing just after
    the last item in the list.
 
    \include qlist.qdoc iterator-invalidation-func-desc
 
    \sa begin(), constEnd()
*/
 
/*! \fn template <typename T> QList<T>::const_iterator QList<T>::end() const
 
    \overload
*/
 
/*! \fn template <typename T> QList<T>::const_iterator QList<T>::cend() const
    \since 5.0
 
    Returns a const \l{STL-style iterators}{STL-style iterator} pointing just
    after the last item in the list.
 
    \include qlist.qdoc iterator-invalidation-func-desc
 
    \sa cbegin(), end()
*/
 
/*! \fn template <typename T> QList<T>::const_iterator QList<T>::constEnd() const
 
    Returns a const \l{STL-style iterators}{STL-style iterator} pointing just
    after the last item in the list.
 
    \include qlist.qdoc iterator-invalidation-func-desc
 
    \sa constBegin(), end()
*/
 
/*! \fn template <typename T> QList<T>::reverse_iterator QList<T>::rbegin()
    \since 5.6
 
    Returns a \l{STL-style iterators}{STL-style} reverse iterator pointing to
    the first item in the list, in reverse order.
 
    \include qlist.qdoc iterator-invalidation-func-desc
 
    \sa begin(), crbegin(), rend()
*/
 
/*! \fn template <typename T> QList<T>::const_reverse_iterator QList<T>::rbegin() const
    \since 5.6
    \overload
*/
 
/*! \fn template <typename T> QList<T>::const_reverse_iterator QList<T>::crbegin() const
    \since 5.6
 
    Returns a const \l{STL-style iterators}{STL-style} reverse iterator pointing
    to the first item in the list, in reverse order.
 
    \include qlist.qdoc iterator-invalidation-func-desc
 
    \sa begin(), rbegin(), rend()
*/
 
/*! \fn template <typename T> QList<T>::reverse_iterator QList<T>::rend()
    \since 5.6
 
    Returns a \l{STL-style iterators}{STL-style} reverse iterator pointing just
    after the last item in the list, in reverse order.
 
    \include qlist.qdoc iterator-invalidation-func-desc
 
    \sa end(), crend(), rbegin()
*/
 
/*! \fn template <typename T> QList<T>::const_reverse_iterator QList<T>::rend() const
    \since 5.6
    \overload
*/
 
/*! \fn template <typename T> QList<T>::const_reverse_iterator QList<T>::crend() const
    \since 5.6
 
    Returns a const \l{STL-style iterators}{STL-style} reverse iterator pointing
    just after the last item in the list, in reverse order.
 
    \include qlist.qdoc iterator-invalidation-func-desc
 
    \sa end(), rend(), rbegin()
*/
 
/*! \fn template <typename T> QList<T>::iterator QList<T>::erase(const_iterator pos)
 
    Removes the item pointed to by the iterator \a pos from the
    list, and returns an iterator to the next item in the list
    (which may be end()).
 
    \include qlist.qdoc shrinking-erase
    \include qlist.qdoc iterator-invalidation-erase
 
    \sa insert(), remove()
*/
 
/*! \fn template <typename T> QList<T>::iterator QList<T>::erase(const_iterator begin, const_iterator end)
 
    \overload
 
    Removes all the items from \a begin up to (but not including) \a
    end. Returns an iterator to the same item that \a end referred to
    before the call.
 
    \include qlist.qdoc shrinking-erase
    \include qlist.qdoc iterator-invalidation-erase
*/
 
/*! \fn template <typename T> T& QList<T>::first()
 
    Returns a reference to the first item in the list. This
    function assumes that the list isn't empty.
 
    \sa last(), isEmpty(), constFirst()
*/
 
/*! \fn template <typename T> const T& QList<T>::first() const
 
    \overload
*/
 
/*! \fn template <typename T> const T& QList<T>::constFirst() const
    \since 5.6
 
    Returns a const reference to the first item in the list. This
    function assumes that the list isn't empty.
 
    \sa constLast(), isEmpty(), first()
*/
 
/*! \fn template <typename T> T& QList<T>::last()
 
    Returns a reference to the last item in the list. This function
    assumes that the list isn't empty.
 
    \sa first(), isEmpty(), constLast()
*/
 
/*! \fn template <typename T> const T& QList<T>::last() const
 
    \overload
*/
 
/*! \fn template <typename T> const T& QList<T>::constLast() const
    \since 5.6
 
    Returns a const reference to the last item in the list. This function
    assumes that the list isn't empty.
 
    \sa constFirst(), isEmpty(), last()
*/
 
/*! \fn template <typename T> T QList<T>::value(qsizetype i) const
 
    Returns the value at index position \a i in the list.
 
    If the index \a i is out of bounds, the function returns a
    \l{default-constructed value}. If you are certain that \a i is within
    bounds, you can use at() instead, which is slightly faster.
 
    \sa at(), operator[]()
*/
 
/*! \fn template <typename T> T QList<T>::value(qsizetype i, parameter_type defaultValue) const
 
    \overload
 
    If the index \a i is out of bounds, the function returns \a defaultValue.
*/
 
/*! \fn template <typename T> void QList<T>::push_back(parameter_type value)
 
    This function is provided for STL compatibility. It is equivalent
    to append(\a value).
*/
 
/*! \fn template <typename T> void QList<T>::push_back(rvalue_ref value)
    \since 5.6
    \overload
*/
 
/*!
    \fn template <typename T> void QList<T>::push_front(parameter_type value)
    \fn template <typename T> void QList<T>::push_front(rvalue_ref value)
 
    This function is provided for STL compatibility. It is equivalent
    to prepend(\a value).
*/
 
/*! \fn template <typename T> void QList<T>::pop_front()
 
    This function is provided for STL compatibility. It is equivalent
    to removeFirst().
*/
 
/*! \fn template <typename T> void QList<T>::pop_back()
 
    This function is provided for STL compatibility. It is equivalent
    to removeLast().
*/
 
/*! \fn template <typename T> T& QList<T>::front()
 
    This function is provided for STL compatibility. It is equivalent
    to first().
*/
 
/*! \fn template <typename T> QList<T>::const_reference QList<T>::front() const
 
    \overload
*/
 
/*! \fn template <typename T> QList<T>::reference QList<T>::back()
 
    This function is provided for STL compatibility. It is equivalent
    to last().
*/
 
/*! \fn template <typename T> QList<T>::const_reference QList<T>::back() const
 
    \overload
*/
 
/*! \fn template <typename T> void QList<T>::shrink_to_fit()
    \since 5.10
 
    This function is provided for STL compatibility. It is equivalent
    to squeeze().
*/
 
/*! \fn template <typename T> bool QList<T>::empty() const
 
    This function is provided for STL compatibility. It is equivalent
    to isEmpty(), returning \c true if the list is empty; otherwise
    returns \c false.
*/
 
/*! \fn template <typename T> QList<T> &QList<T>::operator+=(const QList<T> &other)
 
    Appends the items of the \a other list to this list and
    returns a reference to this list.
 
    \sa operator+(), append()
*/
 
/*! \fn template <typename T> QList<T> &QList<T>::operator+=(QList<T> &&other)
    \since 6.0
 
    \overload
 
    \sa operator+(), append()
*/
 
/*! \fn template <typename T> void QList<T>::operator+=(parameter_type value)
 
    \overload
 
    Appends \a value to the list.
 
    \sa append(), operator<<()
*/
 
/*! \fn template <typename T> void QList<T>::operator+=(rvalue_ref value)
    \since 5.11
 
    \overload
 
    \sa append(), operator<<()
*/
 
/*!
    \fn template <typename T> QList<T> QList<T>::operator+(const QList<T> &other) const &
    \fn template <typename T> QList<T> QList<T>::operator+(const QList<T> &other) &&
    \fn template <typename T> QList<T> QList<T>::operator+(QList<T> &&other) const &
    \fn template <typename T> QList<T> QList<T>::operator+(QList<T> &&other) &&
 
    Returns a list that contains all the items in this list
    followed by all the items in the \a other list.
 
    \sa operator+=()
*/
 
/*! \fn template <typename T> QList<T> &QList<T>::operator<<(parameter_type value)
 
    Appends \a value to the list and returns a reference to this list.
 
    \sa append(), operator+=()
*/
 
/*! \fn template <typename T> QList<T> &QList<T>::operator<<(rvalue_ref value)
    \since 5.11
 
    \overload
 
    \sa append(), operator+=()
*/
 
 
/*! \fn template <typename T> QList<T> &QList<T>::operator<<(const QList<T> &other)
 
    Appends \a other to the list and returns a reference to the list.
*/
 
/*! \fn template <typename T> QList<T> &QList<T>::operator<<(QList<T> &&other)
    \since 6.0
 
    \overload
*/
 
/*! \class QList::iterator
    \inmodule QtCore
    \brief Provides an STL-style non-const iterator for QList and QStack.
 
    QList provides both \l{STL-style iterators} and \l{Java-style
    iterators}.
 
//! [iterator-invalidation-class-desc]
    \warning Iterators on implicitly shared containers do not work
    exactly like STL-iterators. You should avoid copying a container
    while iterators are active on that container. For more information,
    read \l{Implicit sharing iterator problem}.
 
    \warning Iterators are invalidated when QList is modified. Consider that all
    iterators are invalidated by default. Exceptions to this rule are explicitly
    documented.
//! [iterator-invalidation-class-desc]
 
    \sa QList::begin(), QList::end(), QList::const_iterator, QMutableListIterator
*/
 
/*! \class QList::const_iterator
    \inmodule QtCore
    \brief Provides an STL-style const iterator for QList and QStack.
 
    QList provides both \l{STL-style iterators} and \l{Java-style
    iterators}.
 
    \include qlist.qdoc iterator-invalidation-class-desc
 
    \sa QList::constBegin(), QList::constEnd(), QList::iterator, QListIterator
*/
 
/*! \typedef QList::reverse_iterator
    \since 5.6
 
    The QList::reverse_iterator typedef provides an STL-style non-const
    reverse iterator for QList.
 
    \include qlist.qdoc iterator-invalidation-class-desc
 
    \sa QList::rbegin(), QList::rend(), QList::const_reverse_iterator, QList::iterator
*/
 
/*! \typedef QList::const_reverse_iterator
    \since 5.6
 
    The QList::const_reverse_iterator typedef provides an STL-style const
    reverse iterator for QList.
 
    \include qlist.qdoc iterator-invalidation-class-desc
 
    \sa QList::rbegin(), QList::rend(), QList::reverse_iterator, QList::const_iterator
*/
 
/*! \typedef QList::Iterator
 
    Qt-style synonym for QList::iterator.
*/
 
/*! \typedef QList::ConstIterator
 
    Qt-style synonym for QList::const_iterator.
*/
 
/*! \typedef QList::const_pointer
 
    Provided for STL compatibility.
*/
 
/*! \typedef QList::const_reference
 
    Provided for STL compatibility.
*/
 
/*! \typedef QList::difference_type
 
    Provided for STL compatibility.
*/
 
/*! \typedef QList::pointer
 
    Provided for STL compatibility.
*/
 
/*! \typedef QList::reference
 
    Provided for STL compatibility.
*/
 
/*! \typedef QList::size_type
 
    Provided for STL compatibility.
*/
 
/*! \typedef QList::value_type
 
    Provided for STL compatibility.
*/
 
/*! \typedef QList::parameter_type
 
*/
 
/*! \typedef QList::rvalue_ref
 
*/
 
/*! \fn template <typename T> QList<T> QList<T>::toList() const
    \fn template <typename T> QList<T> QList<T>::toVector() const
    \deprecated
 
    A no-op in Qt 6. Provided for backwards compatibility with
    Qt 5, where QList and QVector where two different types.
 
    Returns this list.
*/
 
/*! \fn template <typename T> QList<T> QList<T>::fromList(const QList<T> &list)
    \fn template <typename T> QList<T> QList<T>::fromVector(const QList<T> &list)
    \deprecated
 
    A no-op in Qt 6. Provided for backwards compatibility with
    Qt 5, where QList and QVector were two different types.
 
    Returns this list.
*/
 
/*! \fn template <typename T> QDataStream &operator<<(QDataStream &out, const QList<T> &list)
    \relates QList
 
    Writes the list \a list to stream \a out.
 
    This function requires the value type to implement \c operator<<().
 
    \sa{Serializing Qt Data Types}{Format of the QDataStream operators}
*/
 
/*! \fn template <typename T> QDataStream &operator>>(QDataStream &in, QList<T> &list)
    \relates QList
 
    Reads a list from stream \a in into \a list.
 
    This function requires the value type to implement \c operator>>().
 
    \sa{Serializing Qt Data Types}{Format of the QDataStream operators}
*/
 
/*! \fn template <typename T, typename AT> qsizetype erase(QList<T> &list, const AT &t)
    \relates QList
    \since 6.1
 
    Removes all elements that compare equal to \a t from the
    list \a list. Returns the number of elements removed, if any.
 
    \note Unlike QList::removeAll, \a t is not allowed to be a
    reference to an element inside \a list. If you cannot be sure that
    this is not the case, take a copy of \a t and call this function
    with the copy.
 
    \sa QList::removeAll(), erase_if
*/
 
/*! \fn template <typename T, typename Predicate> qsizetype erase_if(QList<T> &list, Predicate pred)
    \relates QList
    \since 6.1
 
    Removes all elements for which the predicate \a pred returns true
    from the list \a list. Returns the number of elements removed, if
    any.
 
    \sa erase
*/
 
/*! \fn template <typename T> QList<T>::assign(qsizetype n, parameter_type t)
    \since 6.6
 
    Replaces the contents of this list with \a n copies of \a t.
 
    The size of this list will be equal to \a n.
 
    This function will only allocate memory if \a n exceeds the capacity of the
    list or this list is shared.
*/
 
/*! \fn template <typename T> template <typename InputIterator, if_input_iterator<InputIterator>> QList<T>::assign(InputIterator first, InputIterator last)
    \since 6.6
 
    Replaces the contents of this list with a copy of the elements in the
    iterator range [\a first, \a last).
 
    The size of this list will be equal to the number of elements in the
    range [\a first, \a last).
 
    This function will only allocate memory if the number of elements in the
    range exceeds the capacity of this list or this list is shared.
 
    \note This function overload only participates in overload resolution if
    \c InputIterator meets the requirements of a
    \l {https://en.cppreference.com/w/cpp/named_req/InputIterator} {LegacyInputIterator}.
 
    \note The behavior is undefined if either argument is an iterator into
    *this.
*/
 
/*! \fn template <typename T> QList<T>::assign(std::initializer_list<T> l)
    \since 6.6
 
    Replaces the contents of this list with a copy of the elements of
    \a l.
 
    The size of this list will be equal to the number of elements in
    \a l.
 
    This function only allocates memory if the number of elements in \a l
    exceeds the capacity of this list or this list is shared.
*/